During this grant period we propose to study the localization of antigenic sites on the surface of various pathogenic rickettsial including Rickettsia tsutsuganushi, R. rickettsia, R. mooseri, and R. prowazeki by immunoferritin labelling. These will be examined by electron microscopy and the distribution and sites of the specific antigens will be characterized. Along similar lines, the nature of the surface labelling of rickettsial with cationic electron dense markers such as ruthenium red and cationized ferritin will be studied. The normal cell turnover time of the gut epithelial cells to determine why lice suffer an early death due to infection but not the flea will be attempted by light and electron microscope autoradiography. Finally our study of louse mycetome ultrastructure and presence or absence of indigenous rickettsial will be compared to the symbionts common in flea tissues.